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Abstract:

A radiation image acquisition device includes: a radiation source which
emits radiation; a wavelength conversion member of a flat plate shape
which generates scintillation light according to incidence of the
radiation emitted from the radiation source and transmitted by an object;
first imaging means which condenses and images the scintillation light
emitted from an entrance surface for the radiation in the wavelength
conversion member in a direction of a normal to the entrance surface; and
second imaging means which condenses and images the scintillation light
emitted from a surface opposite to the entrance surface in the wavelength
conversion member in a direction of a normal to the opposite surface.

Claims:

1. A radiation image acquisition device comprising: a radiation source
which emits radiation; a wavelength conversion member of a flat plate
shape which generates scintillation light according to incidence of the
radiation emitted from the radiation source and transmitted by an object;
first imaging means which condenses and images the scintillation light
emitted from an entrance surface for the radiation in the wavelength
conversion member in a direction of a normal to the entrance surface; and
second imaging means which condenses and images the scintillation light
emitted from a surface opposite to the entrance surface in the wavelength
conversion member in a direction of a normal to the opposite surface.

2. The radiation image acquisition device according to claim 1, wherein
each of the first imaging means and the second imaging means has: a
condensing lens unit for condensing the scintillation light emitted from
the wavelength conversion member; and an imaging unit for imaging the
scintillation light thus condensed.

3. The radiation image acquisition device according to claim 1, wherein
the radiation source is arranged so that an angle between an optical axis
of the radiation source and the entrance surface is larger than 0.degree.
and smaller than 90.degree., and wherein the first imaging means is
arranged on the normal to the entrance surface.

4. The radiation image acquisition device according to claim 1, wherein
the radiation source is arranged on the normal to the entrance surface,
and wherein the first imaging means is arranged at a position off the
normal to the entrance surface so as to condense the scintillation light
via a reflecting mirror arranged between the wavelength conversion member
and the radiation source.

5. The radiation image acquisition device according to claim 1, wherein
the second imaging means is arranged at a position off the normal to the
opposite surface so as to condense the scintillation light via a
reflecting mirror arranged on the normal to the opposite surface.

6. The radiation image acquisition device according to claim 1, wherein a
tapered fiber is arranged between the opposite surface of the wavelength
conversion member and the second imaging means so as to face the opposite
surface.

7. The radiation image acquisition device according to claim 1, wherein
the object is a semiconductor device, said radiation image acquisition
device being applied to a semiconductor failure inspection device an
inspection target of which is the semiconductor device.

Description:

[0002] There is the conventionally known apparatus for applying X-rays
emitted from an X-ray source and transmitted by an imaging object, onto a
scintillator of a flat plate shape, detecting visible light
(scintillation light) generated in the scintillator, by solid-state
photodetectors laid on both surfaces of the scintillator, and
superimposing image signals from the respective solid-state
photodetectors on each other to acquire a radiation image, as described
in Patent Literature 1 below. In this apparatus, the photodetector
elements are coupled to the X-ray entrance surface and to the back
surface behind it in the scintillator and the visible light is detected
by each of the entrance-surface-side photodetector element and the
back-surface-side photodetector element, thereby increasing efficiency of
detection of the visible light.

[0004] The apparatus for detecting the scintillation light on the both
surfaces of the scintillator as described above can acquire radiation
images in different energy bands on the entrance surface side and on the
back surface side behind it, so as to enable acquisition of so-called
dual-energy images

[0005] In the foregoing conventional apparatus, however, the radiation
transmitted by the object passes through the entrance-surface-side
photodetector element to reach the scintillator, and for this reason,
radiation in a relatively low energy band is absorbed by the
entrance-surface-side photodetector element. For example, when the object
is formed of a lightweight atom, the radiation transmitted by the object
can be absorbed by the entrance-surface-side photodetector element. As
described above, the conventional apparatus has the problem that the
radiation transmitted by the object is affected by the
entrance-surface-side photodetector element.

[0006] It is therefore an object of the present invention to provide a
radiation image acquisition device capable of acquiring radiation images
in different energy bands while reducing the influence on the radiation
transmitted by the object.

Solution to Problem

[0007] A radiation image acquisition device according to one aspect of the
present invention includes: a radiation source which emits radiation; a
wavelength conversion member of a flat plate shape which generates
scintillation light according to incidence of the radiation emitted from
the radiation source and transmitted by an object; first imaging means
which condenses and images the scintillation light emitted from an
entrance surface for the radiation in the wavelength conversion member in
a direction of a normal to the entrance surface; and second imaging means
which condenses and images the scintillation light emitted from a surface
opposite to the entrance surface in the wavelength conversion member in a
direction of a normal to the opposite surface.

[0008] In the radiation image acquisition device according to the one
aspect of the present invention, the first imaging means and the second
imaging means condense and image the respective scintillation light beams
emitted from the entrance surface for the radiation and the opposite
surface behind it in the wavelength conversion member. This realizes
dual-energy imaging to acquire radiation images in different energy
bands. In this connection, the first imaging means is arranged at a
position apart from the wavelength conversion member, in order to
condense the scintillation light emitted from the entrance surface.
Therefore, the radiation image acquisition device can have the
configuration wherein no imaging means is interposed between the object
and the wavelength conversion member, thereby avoiding an incident such
that the imaging means affects the radiation transmitted by the object.
Accordingly, it is feasible to reduce the influence on the radiation
transmitted by the object. Furthermore, since the first imaging means and
the second imaging means condense the scintillation light beams emitted
from the entrance surface and from the opposite surface behind it in the
directions of the respective normals thereto, they both can acquire
radiation images with no perspective, which facilitates an operation
between the images on the entrance surface side and on the opposite
surface side.

[0009] The radiation image acquisition device may be configured in a mode
such that each of the first imaging means and the second imaging means
has: a condensing lens unit for condensing the scintillation light
emitted from the wavelength conversion member; and an imaging unit for
imaging the scintillation light thus condensed. In this case, the
scintillation light is condensed with focus on each of the entrance
surface and the opposite surface of the wavelength conversion member,
which enables acquisition of bright radiation images with good energy
separation.

[0010] The radiation image acquisition device may be configured in a mode
such that the radiation source is arranged so that an angle between an
optical axis of the radiation source and the entrance surface is larger
than 0° and smaller than 90°, and that the first imaging
means is arranged on the normal to the entrance surface. In this case,
the first imaging means can directly condense the scintillation light in
the direction of the normal to the entrance surface, and the first
imaging means can be arranged off the optical axis of the radiation
source. Therefore, the aforementioned operational effect can be readily
achieved and the first imaging means can be prevented from being exposed
to the radiation, which can suppress generation of noise inside the first
imaging means.

[0011] The radiation image acquisition device may be configured in a mode
such that the radiation source is arranged on the normal to the entrance
surface and that the first imaging means is arranged at a position off
the normal to the entrance surface so as to condense the scintillation
light via a reflecting mirror arranged between the wavelength conversion
member and the radiation source. In this case, since the radiation source
is arranged on the normal to the entrance surface, no perspective is made
in a projection image on the wavelength conversion member, which
eliminates a need for an operation to correct for a perspective of the
projection image. Furthermore, the first imaging means can be prevented
from being exposed to the radiation, which can suppress generation of
noise inside the first imaging means.

[0012] The radiation image acquisition device may be configured in a mode
such that the second imaging means is arranged at a position off the
normal to the opposite surface so as to condense the scintillation light
via a reflecting mirror arranged on the normal to the opposite surface.
In this case, the second imaging means can be prevented from being
exposed to the radiation, which can suppress generation of noise inside
the second imaging means. Furthermore, this configuration permits
adjustment of optical path lengths from the wavelength conversion member
to the first and second imaging means, which facilitates position
alignment of the first and second imaging means. As a consequence of
this, it becomes easier to match imaging conditions of the first and
second imaging means (e.g., simultaneity of imaging times and identity of
imaging positions).

[0013] The radiation image acquisition device may be configured in a mode
such that a tapered fiber is arranged between the opposite surface of the
wavelength conversion member and the second imaging means so as to face
the opposite surface. In this case, the tapered fiber can condense the
scintillation light on the opposite surface side at a high light
condensing efficiency. Furthermore, the tapered fiber blocks the
radiation whereby the second imaging means can be prevented from being
exposed to the radiation.

[0014] The radiation image acquisition device may be configured in a mode
such that the object is a semiconductor device and that the radiation
image acquisition device is applied to a semiconductor failure inspection
device an inspection target of which is the semiconductor device. In this
case, since the radiation transmitted by the semiconductor device as the
inspection target is not cut by the imaging unit (imaging device for
acquisition of image), the inspection device can detect a failure or the
like of the semiconductor device with high accuracy.

Advantageous Effect of Invention

[0015] The one aspect of the present invention enables the acquisition of
radiation detection images in different energy bands and the reduction of
the influence on the radiation transmitted by the object.

BRIEF DESCRIPTION OF DRAWINGS

[0016] FIG. 1 is a front view of the radiation image acquisition device
according to the first embodiment of the present invention.

[0017]FIG. 2 is an explanatory drawing for explaining a perspective of a
projection image in the radiation image acquisition device shown in FIG.
1.

[0018]FIG. 3 is a front view of the radiation image acquisition device
according to the second embodiment of the present invention.

[0019]FIG. 4 is an explanatory drawing for explaining a projection image
in the radiation image acquisition device shown in FIG. 3.

[0020]FIG. 5 is a front view of the radiation image acquisition device
according to the third embodiment of the present invention.

[0021] FIG. 6 is a front view of the radiation image acquisition device
according to the fourth embodiment of the present invention.

[0022] FIGS. 7(a) and (b) is front views of the radiation image
acquisition devices which are modification examples of the present
invention.

[0023]FIG. 8(a) to (c) is front views of the radiation image acquisition
devices which are modification examples of the present invention.

DESCRIPTION OF EMBODIMENTS

[0024] Embodiments of the present invention will be described below in
detail with reference to the drawings. Identical or equivalent portions
will be denoted by the same reference signs in the description of the
drawings, without redundant description. It is noted that each drawing is
prepared by way of illustration only and is depicted so as to emphasize
each part as object of description in particular. For this reason, the
dimensional ratios of respective members in the drawings are not always
coincident with actual ones.

[0025] As shown in FIG. 1, the radiation image acquisition device 1 is a
device for acquiring a radiation image of an object A, e.g., an
electronic component such as a semiconductor device, or a foodstuff. The
radiation image acquisition device 1 is provided with a radiation source
2 which emits radiation such as white X-rays toward the object A, a
wavelength conversion plate 6 which generates scintillation light
according to incidence of the radiation transmitted by the object A after
emitted from the radiation source 2, a front observation photodetector 3
which condenses and images the scintillation light emitted from an
entrance surface 6a for the radiation in the wavelength conversion plate
6, and a back observation photodetector 4 which condenses and images the
scintillation light emitted from a back surface 6b being a surface
opposite to the entrance surface 6a. These radiation source 2, wavelength
conversion plate 6, front observation photodetector 3, and back
observation photodetector 4 are housed in a housing not shown and fixed
in the housing.

[0026] The wavelength conversion plate 6 is a wavelength conversion member
of a flat plate shape, e.g., a scintillator of any one of
Gd2O2S:Tb, Gd2O2S:Pr, CsI:Tl, CdWO4, CaWO4,
Gd2SiO5:Ce, Lu0.4Gd1.6SiO5,
Bi4Ge3O12, Lu2SiO5:Ce, Y2SiO5,
YAlO3:Ce, Y2O2S:Tb, YTaO4:Tm, and so on. The
thickness of the wavelength conversion plate 6 is set to an appropriate
value depending upon a radiation energy band detected, in the range of
several 1 μm to several mm.

[0027] The front observation photodetector 3 (which will be referred to
hereinafter as "front detector 3") is an imaging means of an indirect
conversion method that photographs a projection image (radiation
transmission image) of the object A projected on the wavelength
conversion plate 6, from the entrance surface 6a side of the wavelength
conversion plate 6. The front detector 3 is a detector of a lens coupling
type having a condensing lens unit 3a for condensing the scintillation
light emitted from the entrance surface 6a of the wavelength conversion
plate 6, and an imaging unit 3b for imaging the scintillation light
condensed by the condensing lens unit 3a. The condensing lens unit 3a
condenses the scintillation light in a front detector field 13. The
imaging unit 3b to be used herein is, for example, a CMOS sensor, a CCD
sensor, or the like. A light receiving surface of the imaging unit 3b can
be arranged approximately parallel to the entrance surface 6a.

[0028] The back observation photodetector 4 (which will be referred to
hereinafter as "back detector 4") is an imaging means of the indirect
conversion method that photographs a projection image (radiation
transmission image) of the object A projected on the wavelength
conversion plate 6, from the back surface 6b side of the wavelength
conversion plate 6. The back detector 4 is a detector of the lens
coupling type having a condensing lens unit 4a for condensing the
scintillation light emitted from the back surface 6b of the wavelength
conversion plate 6, and an imaging unit 4b for imaging the scintillation
light condensed by the condensing lens unit 4a, and thus it has the same
configuration as the aforementioned front detector 3. The condensing lens
unit 4a condenses the scintillation light in a back detector field 14.
The imaging unit 4b to be used herein is, for example, a CMOS sensor, a
CCD sensor, or the like. A light receiving surface of the imaging unit 4b
can be arranged approximately parallel to the back surface 6b.

[0029] Furthermore, the radiation image acquisition device 1 is provided
with a timing control unit 7 for controlling imaging timing at the front
detector 3 and at the back detector 4, an image processing device 8 for
receiving input image signals from the front detector 3 and from the back
detector 4 and executing a predetermined processing procedure such as
image processing based on each of the input image signals, and a display
device 9 for receiving an input image signal from the image processing
device 18 and displaying a radiation image. The timing control unit 7 and
the image processing device 8 are composed of a computer having a CPU
(Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access
Memory), input/output interfaces, and so on. The display device 9 to be
used herein is a well-known display. The timing control unit 7 and the
image processing device 8 may be configured as a program executed by a
single computer or as respective units provided individually.

[0030] The below will describe the positional relationship among the
aforementioned radiation source 2, wavelength conversion plate 6, front
detector 3, and back detector 4. As shown in FIG. 1, the radiation source
2 is arranged so that an optical axis X of the radiation makes a
predetermined angle θ with respect to a normal B to the entrance
surface 6a of the wavelength conversion plate 6. Namely, the radiation
source 2 faces the object A and the entrance surface 6a and is arranged
at a position off the normal B to the entrance surface 6a. In other
words, the radiation source 2 is arranged so that the angle between the
optical axis X and the entrance surface 6a is larger than 0° and
smaller than 90°. The optical axis X of the radiation here is a
straight line connecting a radiation emission point of the radiation
source 2 and an arbitrary point γ on the entrance surface 6a of the
wavelength conversion plate 6. In the present embodiment, the arbitrary
point γ is set to be a central point of the entrance surface 6a and
in this case, the radiation is radiated with little relative unevenness.
The normal B here is a straight line extending normally to the entrance
surface 6a from an arbitrary point α on the entrance surface 6a. In
the present embodiment, the arbitrary point α is set to be the
central point of the entrance surface 6a and thus the optical axis X of
the radiation and the normal B intersect at the arbitrary point γ
(arbitrary point α) on the entrance surface 6a. It is a matter of
course that the arbitrary point γ and the arbitrary point α
do not have to be coincident with the central point of the entrance
surface 6a and do not have to be the same point, either.

[0031] The front detector 3 is arranged so that an optical axis of the
incorporated condensing lens unit 3a is perpendicular to the entrance
surface 6a, so as to be able to image the scintillation light emitted
from the entrance surface 6a of the wavelength conversion plate 6. In
this configuration, the optical axis of the condensing lens unit 3a is
coincident with the normal B to the entrance surface 6a. Namely, the
front detector 3 faces the entrance surface 6a and is arranged on the
normal B to the entrance surface 6a. Therefore, the front detector 3 can
image the scintillation light emitted in the direction of the normal B to
the entrance surface 6a and thus readily acquire an image without a
significant perspective. The condensing lens unit 3a focuses on the
entrance surface 6a and condenses the scintillation light emitted in the
direction of the normal B from the entrance surface 6a, toward the
imaging unit 3b.

[0032] As described above, the front detector 3 is arranged off the
optical axis X of the radiation source 2. Namely, the front detector 3 is
arranged so as to be located apart from an emission region of the
radiation from the radiation source 2 (which is a region where a
radiation beam 12 exists). This arrangement prevents the front detector 3
from being exposed to the radiation from the radiation source 2 and
prevents a direct conversion signal of radiation from being produced
inside the front detector 3 to generate noise. Furthermore, the front
detector 3 is arranged so that a perpendicular to the entrance surface 6a
of the wavelength conversion plate 6 from the center of the condensing
lens unit 3a is within the range of the entrance surface 6a and so that
it is located above the entrance surface 6a of the wavelength conversion
plate 6. This configuration allows the front detector 3 to detect a
relatively large quantity of scintillation light.

[0033] The back detector 4 is arranged so that an optical axis of the
incorporated condensing lens unit 4a is perpendicular to the back surface
6b, so as to be able to image the scintillation light emitted from the
back surface 6b of the wavelength conversion plate 6. In this
configuration, the optical axis of the condensing lens unit 4a is
coincident with a normal C to the back surface 6b. Namely, the back
detector 4 faces the back surface 6b and is arranged on the normal C to
the back surface 6b. Therefore, the back detector 4 can image the
scintillation light emitted in the direction of the normal C to the back
surface 6b and thus readily acquire an image without a significant
perspective. The normal C here is a straight line extending normally to
the back surface 6b from an arbitrary point β on the back surface
6b. Particularly, in the present embodiment, the arbitrary point β
is set at a central point of the back surface 6b, the arbitrary point
α on the entrance surface 6a and the arbitrary point β on the
back surface 6b are located on the same straight line, and this straight
line is coincident with the normal B and the normal C. The condensing
lens unit 4a focuses on the back surface 6b and condenses the
scintillation light emitted in the direction of the normal C from the
back surface 6b, toward the imaging unit 4b.

[0034] In the radiation image acquisition device 1, an optical path length
from the entrance surface 6a of the wavelength conversion plate 6 to the
front detector 3 is equal to an optical path length from the back surface
6b of the wavelength conversion plate 6 to the back detector 4. The
optical path length from the entrance surface 6a of the wavelength
conversion plate 6 to the front detector 3 may be different from the
optical path length from the back surface 6b of the wavelength conversion
plate 6 to the back detector 4, but in this case, the sizes of the images
need to be matched by image processing or the like.

[0035] The following will describe the operation of the radiation image
acquisition device 1 having the above-described configuration. First, the
timing control unit 7 performs control to make the front detector 3 and
the back detector 4 simultaneously carry out their respective imaging
operations. The imaging of radiation transmission images of the object A
in different energy bands can be implemented based on the imaging timing
control by the timing control unit 7. In more detail, the front detector
3 acquires the radiation transmission image in a relatively low energy
band and the back detector 4 the radiation transmission image in a
relatively high energy band. This operation realizes dual-energy imaging.
It is noted that the radiation image acquisition device 1 is configured
to allow control to make the imaging times of the front detector 3 and
the back detector 4 different from each other. The device may also be
configured to control the front detector 3 and the back detector 4 to
different exposure times and/or different numbers of photos taken
thereby.

[0036] The functions of the front detector 3 and the back detector 4 will
be specifically described in more detail. The front detector 3 detects
fluorescence (scintillation light) resulting from conversion on the side
relatively near the entrance surface 6a. The detection of the
fluorescence resulting from the conversion on the entrance surface 6a
side is characterized by little blurring of fluorescence and high
luminance of fluorescence. This is because the front observation can be
less affected by diffusion and self-absorption inside the wavelength
conversion plate 6. On the other hand, the back detector 4 detects
fluorescence resulting from conversion on the side relatively near the
back surface 6b of the wavelength conversion plate 6. In this case as
well, the observation can be less affected by diffusion and
self-absorption inside the wavelength conversion plate 6.

[0037] Next, the front detector 3 and the back detector 4 output their
respective image signals corresponding to the radiation images on both of
the front and back surfaces, to the image processing device 8. When the
image processing device 8 receives the respective input image signals
from the front detector 3 and from the back detector 4, the image
processing device 8 executes the predetermined processing such as an
inter-image operation, e.g., a differential operation or an addition
operation, based on the input image signals, and outputs an image signal
after the image processing to the display device 9. When the display
device 9 receives the input image signal after the image processing from
the image processing device 8, the display device 9 displays a radiation
image according to the input image signal after the image processing.

[0038]FIG. 2(a) is a perspective view showing the positional relationship
among the radiation source 2, object A, and wavelength conversion plate 6
in the radiation image acquisition device 1, FIG. 2(b) a front view
showing the positional relationship among the radiation source 2, object
A, and wavelength conversion plate 6, and FIG. 2(c) a plan view showing a
projection image D of the object A projected on the wavelength conversion
plate 6. FIG. 2 shows a situation in which the object A is of a 3D shape,
for easier understanding. When the radiation source 2 is arranged at the
position off the normal B to the entrance surface 6a and the optical axis
X of the radiation makes the predetermined angle θ with respect to
the normal B to the entrance surface 6a as shown in FIG. 2(a), a
perspective is made in the projection image D onto the entrance surface
6a, as shown in FIG. 2(c). Since the front detector 3 and the back
detector 4 take respective images of the projection image D from the
directions of the normals B, C, respectively, no perspective is made in
the taken images, which facilitates the operation between the two images
in the image processing device 8. The perspective of the projection image
D is corrected according to needs by the image processing device 8.
Although FIG. 2(a) shows that the main body of the radiation source 2 is
parallel to the optical axis X, for convenience' sake of explanation, the
orientation of arrangement of the radiation source 2 can be optionally
set according to the layout of the device.

[0039] In the radiation image acquisition device 1 of the present
embodiment described above, the front detector 3 and the back detector 4
condense and image the respective scintillation light beams emitted from
the entrance surface 6a and the back surface 6b of the wavelength
conversion plate 6, thereby realizing the dual-energy imaging to acquire
radiation images in different energy bands. In this configuration, the
front detector 3 is arranged at the position apart from the wavelength
conversion plate 6, without any detector interposed between the object A
and the wavelength conversion plate 6. This configuration permits the
device to avoid the incident that the imaging means affects the radiation
transmitted by the object A. Therefore, the influence on the radiation
transmitted by the object A is reduced and the radiation in a low energy
band is suitably detected. In other words, no shadow of detector is cast
on the radiation transmission images, so as to suppress generation of
noise component and cause no attenuation of radiation due to the
detector, thus suppressing reduction of signal components. As a result,
it becomes feasible to make a difference between the low energy band and
the high energy band in the dual-energy imaging larger and to exhibit a
high energy resolution, allowing achievement of higher contrast. This
advantage is prominently demonstrated, particularly, in the case where
the object A is formed of silicon or an atom lighter in weight than
silicon. Namely, even if the object A is formed of a lightweight atom,
the radiation in the low energy band transmitted by the object A is
converted into scintillation light, without being absorbed or attenuated,
and this light is imaged by the front detector 3; therefore, the
radiation image in the low energy band can be acquired with accuracy. In
addition, the low-energy image and the high-energy image can be
simultaneously acquired by a single imaging operation, so as to ensure
simultaneity, reduce an exposure dose, and avoid pixel shifts
(misregistration). The dual-energy imaging can be realized even by means
of the single wavelength conversion plate 6. In addition, the front
detector 3 and the back detector 4 condense the scintillation light beams
emitted in the directions of the normals B, C, respectively, from the
entrance surface 6a and the back surface 6b and thus both can acquire the
radiation images without a perspective, which facilitates the operation
between the images on the entrance surface 6a side and the back surface
6b side.

[0040] When white X-rays are used as the radiation, the low-energy image
and the high-energy image can also be simultaneously acquired by a single
imaging operation of white X-rays, so as to ensure simultaneity, reduce
an exposure dose, and avoid pixel shifts (misregistration).

[0041] As the condensing lens unit 3a and the condensing lens unit 4a
condense the light with focus on each of the entrance surface 6a and the
back surface 6b of the wavelength conversion plate 6, bright radiation
images can be acquired with good energy separation.

[0042] Since the front detector 3 directly condenses the scintillation
light in the direction of the normal B to the entrance surface 6a and the
front detector 3 is arranged off the optical axis X of the radiation
source 2, the aforementioned operational effect is readily achieved and
the front detector 3 is prevented from being exposed to the radiation, so
as to suppress generation of noise inside the front detector 3.

[0043]FIG. 3 is a front view of the radiation image acquisition device
according to the second embodiment. The radiation image acquisition
device 1A shown in FIG. 3 is different from the radiation image
acquisition device 1 shown in FIG. 1 in that the radiation source 2 is
arranged on the normal B to the entrance surface 6a and in that the front
detector 3 is arranged at a position off the normal B to the entrance
surface 6a so as to condense the scintillation light via a reflecting
mirror 15 arranged on the normal B (optical axis X) between the
wavelength conversion plate 6 and the radiation source 2. FIG. 3 is
depicted without illustration of the timing control unit 7, image
processing device 8, and display device 9. FIGS. 5 to 8 are also depicted
similarly without illustration of these components.

[0044] The configuration of the radiation image acquisition device 1A will
be described more specifically. The radiation source 2 is arranged so
that the optical axis X of the radiation is coincident with the normal B
to the entrance surface 6a. The reflecting mirror 15 is arranged so that
its reflective surface 15a makes a predetermined angle (e.g., 45°)
with respect to the direction of the normal B so as to reflect the
scintillation light emitted in the direction of the normal B from the
entrance surface 6a, into a predetermined direction relative to the
normal B. The reflecting mirror 15 to be used herein is, for example, an
optical mirror that transmits the radiation. The front detector 3 is
arranged so that an angle between the optical axis of the incorporated
condensing lens unit 3a and the reflective surface 15a is equal to the
angle between the normal B and the reflective surface 15a. This
condensing lens unit 3a condenses the scintillation light emitted in the
direction of the normal B from the entrance surface 6a and reflected into
the predetermined direction relative to the normal B by the reflecting
mirror 15, toward the imaging unit 3b.

[0045] As described above, the front detector 3 is arranged so as to be
apart from the radiation emission region from the radiation source 2 (the
region where the radiation beam 12 exists). This arrangement prevents the
front detector 3 from being exposed to the radiation from the radiation
source 2, and thus prevents a direct conversion signal of radiation from
being produced inside the front detector 3 to generate noise.
Furthermore, the optical path length from the entrance surface 6a of the
wavelength conversion plate 6 to the front detector 3 may be set equal to
the optical path length from the back surface 6b of the wavelength
conversion plate 6 to the back detector 4.

[0046]FIG. 4(a) is a perspective view showing the positional relationship
among the radiation source 2, object A, and wavelength conversion plate 6
in the radiation image acquisition device 1A, FIG. 4(b) a front view
showing the positional relationship among the radiation source 2, object
A, and wavelength conversion plate 6, and FIG. 4(c) a plan view showing a
projection image E of the object A projected on the wavelength conversion
plate 6. FIG. 4 shows a situation in which the object A is of a 3D shape,
for easier understanding. When the radiation source 2 is arranged on the
normal B to the entrance surface 6a and the optical axis X of the
radiation is coincident with the normal B to the entrance surface 6a as
shown in FIG. 4(a), no perspective is made in the projection image E onto
the entrance surface 6a, as shown in FIG. 4(c). Since the front detector
3 takes an image of the projection image E from the direction of the
normal B via the reflecting mirror 15 and the back detector 4 takes an
image of the projection image E from the direction of the normal C, no
perspective is made in the taken images, which facilitates the operation
between the two images in the image processing device 8. Since there is
no perspective in the projection image E, no perspective correction is
needed in the image processing device 8. Since the reflecting mirror 15
is arranged on the optical axis X of the radiation source 2 in the
radiation image acquisition device 1A, the reflecting mirror 15 absorbs
some radiation.

[0047] The radiation image acquisition device 1A achieves the same
operational effect as the radiation image acquisition device 1 does.
Since the radiation source 2 is arranged on the normal B to the entrance
surface 6a, no perspective is made in the projection image E onto the
wavelength conversion plate 6 and thus there is no need for an operation
for correction for a perspective of the projection image E. Furthermore,
the front detector 3 is prevented from being exposed to the radiation,
which prevents generation of noise inside the front detector 3.

[0048]FIG. 5 is a front view of the radiation image acquisition device
according to the third embodiment. The radiation image acquisition device
1B shown in FIG. 5 is different from the radiation image acquisition
device 1 of the first embodiment shown in FIG. 1 in that the back
detector 4 is arranged at a position off the normal C to the back surface
6b so as to condense the scintillation light via a reflecting mirror 16
arranged on the normal C. More specifically, the reflecting mirror 16 is
arranged so that its reflective surface 16a makes a predetermined angle
(e.g., 45°) with respect to the direction of the normal C and thus
it reflects the scintillation light emitted in the direction of the
normal C from the back surface 6b, into a predetermined direction with
respect to the normal C. The reflecting mirror 16 to be used herein is,
for example, an optical mirror or a prism. The back detector 4 is
arranged so that an angle between the optical axis of the incorporated
condensing lens unit 4a and the reflective surface 16a is equal to the
angle between the normal C and the reflective surface 16a. This
condensing lens unit 4a condenses the scintillation light emitted in the
direction of the normal C from the back surface 6b and reflected in the
predetermined direction relative to the normal C by the reflecting mirror
16, toward the imaging unit 4b.

[0049] As described above, the back detector 4 is arranged so as to be
apart from the radiation emission region from the radiation source 2 (the
region where the radiation beam 12 exists). This arrangement prevents the
back detector 4 from being exposed to the radiation from the radiation
source 2, and thus prevents a direct conversion signal of radiation from
being produced inside the back detector 4 to generate noise. Furthermore,
the optical path length from the entrance surface 6a of the wavelength
conversion plate 6 to the front detector 3 may be set equal to the
optical path length from the back surface 6b of the wavelength conversion
plate 6 to the back detector 4.

[0050] The radiation image acquisition device 1B achieves the same
operational effect as the radiation image acquisition devices 1 and 1A
do. In addition, the back detector 4 is prevented from being exposed to
the radiation, which prevents generation of noise inside the back
detector 4. Furthermore, the optical path lengths from the wavelength
conversion plate 6 to the front detector 3 and the back detector 4 are
allowed to adjust, which facilitates position alignment of the first and
second imaging means. As a consequence of this, it becomes easier to
match the imaging conditions of the first and second imaging means (e.g.,
simultaneity of imaging times and identity of imaging positions).

[0051] FIG. 6 is a front view of the radiation image acquisition device
according to the fourth embodiment. The radiation image acquisition
device 1C shown in FIG. 6 is different from the radiation image
acquisition device 1 of the first embodiment shown in FIG. 1 in that a
tapered fiber 17 is arranged so as to face the back surface 6b between
the back surface 6b and the back detector 4. More specifically, the
tapered fiber 17 is arranged so that its axis is coincident with the
normal C to the back surface 6b, so as to guide the scintillation light
emitted in the direction of the normal C from the back surface 6b, to the
condensing lens unit of the back detector 4. This tapered fiber 17 and
the back detector 4 constitute a fiber coupling detector 18.

[0052] The radiation image acquisition device 1C achieves the same
operational effect as the radiation image acquisition devices 1, 1A, and
1B do. The tapered fiber 17 condenses the scintillation light on the back
surface 6b side at a high light condensing efficiency. An ordinary
fluorescent image tends to become dark on the back surface 6b side of the
wavelength conversion plate 6, but a loss in the optical system can be
reduced by adopting the fiber coupling detector 18. Furthermore, the
tapered fiber 17 blocks the radiation from the radiation source 2, so as
to prevent exposure of the back detector 4 thereto.

[0053] The above described the embodiments of the present invention but
the present invention is by no means intended to be limited to the above
embodiments. For example, various modifications as shown in FIG. 7 may be
adopted in the configuration wherein the radiation source 2 is arranged
on the normal B to the entrance surface 6a. Specifically, as shown in
FIG. 7(a), the radiation image acquisition device 1D may be so configured
that the reflecting mirror 15 is arranged on the entrance surface 6a side
and that the reflecting mirror 16 is arranged on the back surface 6b
side. Furthermore, as shown in FIG. 7(b), the radiation image acquisition
device 1E may be so configured that the reflecting mirror 15 is arranged
on the entrance surface 6a side and that the fiber coupling detector 18
is arranged on the back surface 6b side.

[0054] Furthermore, various modifications as shown in FIG. 8 can also be
adopted in the configuration wherein the radiation source 2 is arranged
at the position off the normal B to the entrance surface 6a.
Specifically, as shown in FIG. 8(a), the radiation image acquisition
device 1F may be so configured that the reflecting mirror 15 is arranged
on the entrance surface 6a side and that the back detector 4 is arranged
on the normal C to the back surface 6b. Moreover, as shown in FIG. 8(b),
the radiation image acquisition device 1G may be so configured that the
reflecting mirror 15 is arranged on the entrance surface 6a side and that
the reflecting mirror 16 is arranged on the back surface 6b side.
Furthermore, as shown in FIG. 8(c), the radiation image acquisition
device 1H may be so configured that the reflecting mirror 15 is arranged
on the entrance surface 6a side and that the fiber coupling detector 18
is arranged on the back surface 6b side.

[0055] The above embodiments, in the cases using the reflecting mirror 15
or 16, described the examples wherein the reflecting mirror 15, 16 was
arranged at the angle of 45° with respect to the normal B, C and
wherein the optical axis of the condensing lens unit was perpendicular to
the normal B, C, but, without having to be limited to this arrangement,
the angle of the reflecting mirror 15, 16 and the arrangement of the
front detector 3 and the back detector 4 may be optionally modified
according to the layout in the device.

[0056] The above embodiments described the examples wherein the arbitrary
point γ and the arbitrary point α coincided on the entrance
surface 6a, but they may be located at different positions on the
entrance surface 6a. In this case, the radiation source 2 may be arranged
so that the optical axis X is perpendicular to the entrance surface 6a
and the front detector 3 may be arranged so that the optical axis of the
condensing lens unit 3a is perpendicular to the entrance surface 6a.

[0057] Namely, the optical axis X of the radiation source 2 and the
optical axis of the condensing lens unit 3a are parallel to each other
and a separation distance between these optical axes becomes equal to a
separation distance between the point γ and the point α. In
this configuration, the front detector 3 can condense and image the
scintillation light emitted in the direction of the normal to the
entrance surface 6a.

[0058] The above embodiments used the lens coupling type detectors as
detectors, but the condensing lens unit and the imaging unit may be
provided as separate members.

[0059] An effective application is such that the object A is a
semiconductor device and the radiation image acquisition device of the
above embodiment is applied to a semiconductor failure inspection device
an inspection target of which is the semiconductor device. In this case,
the radiation transmitted by the semiconductor device as the inspection
target is not cut by the imaging unit (imaging device for acquisition of
image) and thus a failure or the like of the semiconductor device can be
detected with accuracy.

INDUSTRIAL APPLICABILITY

[0060] The one aspect of the present invention enables the acquisition of
radiation images in different energy bands and the reduction of the
influence on the radiation transmitted by the object.